After floral induction, the first step in the development of flowers is the generation of floral meristems. At least three genes, CAULIFLOWER, APETALA1, and LEAFY, are necessary for the specification of floral meristem identity in Arabidopsis. This investigator has recently isolated the CAULIFLOWER and APETALA1 genes. This proposal describes a combined genetic and molecular approach for determining how CAULIFLOWER interacts with other genes to promote flowering. The investigator proposes to isolate and characterize an allelic series of cal mutants and analyze the resulting phenotypes by scanning electron microscopy. The transcriptional regulation of CAULIFLOWER will be investigated by determining the spatial and temporal pattern of expression in a variety of mutant backgrounds. Additional studies will determine if the CAULIFLOWER protein interacts directly with APETALA1, and will identify the DNA sequences to which CAULIFLOWER specifically binds. Further studies will investigate the cis- and trans-acting factors needed to promote floral meristem-specific expression of CAL, and will determine the molecular basis for the functional redundancy of CAL and AP1. These studies will be integrated into efforts to understand the role of APETALA1 and should lead to significant contributions towards understanding the genetic and molecular control of floral meristem specification. The cauliflower phenotype in Arabidopsis is strikingly similar to the anomalous inflorescence structures produced in the dinner table cauliflower, Brassica oleracea. Since Arabidopsis and Brassica are closely related plant species, and since the phenotypes of these mutants is similar, the investigator will use the cloned CAL and AP1 genes to investigate the molecular basis of the cauliflower phenotype. Finally, since the cauliflower phenotype has been described in plants that are distantly related to Arabidopsis, and since the CAULIFLOWER gene has not been isolated from any other plant s pecies, the characterization of this gene should yield significant insights into its role in diverse plant systems.
